Those marked (*) are archaic terms, used by Shakespeare for instance.
Against type: playing a different character than expected
Antagonist: a character that hinders the protagonist from achieving their goals
Anti-naturalist: acting style in which the audience is kept aware that they are watching a performance rather than reality (see Brectian Acting)
Beat: The smallest division of action in a play. The length of time necessary for a character to play an "Objective" (also called "Intention") from beginning to end.
Brechtian acting: acting style in which the actors purposefully try to alienate the audience from the characters in order to constantly remind them they are watching a play, based on the theories of Bertolt Brecht
Blocking: an actor's movement around a set, or the notations regarding movement in an actor's script.
Cast: the actors in a play; the characters; to choose the actors
Cold reading: a reading aloud from a script or other text without any rehearsal, usually in the context of an audition or workshop.
Community theatre: performance by amateurs, usually unpaid, as opposed to professional theatre
Cover: to make up dialogue and or blocking due to a mistake or accident onstage without breaking character.
Curtain call, Walkdown: at the end of a performance, when the actors come to the front of the stage to bow while the audience claps
Dialogue: a reciprocal conversation between two or more persons; the speaking lines of a script
Distanciation: in Brechtian performance, when actors maintain distance from their character by reminding the audience through often stylized gestures or behavior that they are simply people pretending, instead of trying to identify with their "character".
Downstage: towards the front of the stage; the half of the stage that is nearest to the audience
Dress Circle: In some theatres, a shallow gallery level above the main seating.
Dramatist: the author of a play
Emotional memory: in Method acting, when an actor attempts to draw upon memories of prior emotions to match the emotions of their character
Exeunt *: a stage direction for more than one to person exit, from the Latin exire, "to go out"
Exeunt omnes *: a stage direction meaning all the cast exit
Exit: a stage direction which specifies which person goes off stage
Fourth wall: an imaginary surface at the edge of the stage through with the audience watches a performance
Full house, Packed house, Sold out: when all of the seats are filled; when the entire audience section is filled to capacity
Gallery, Gods: the highest section of the theatre; a section at the back or sides without seats where people can stand to watch a performance, usually raised
Ghost Light: A light left on the stage overnight and/or when the stage is not in use for safety.
Intention: a single, temporary desire or goal that arises in a character within a scene. (Also called "Objective".)
Issue: to leave the stage
Masking: drapery or flats used to frame the stage
Method acting: acting style in which the ideal of a "true"( or "real") moment or impulse is valued most highly; the actors try to feel the emotions of the character so that the actors' choices and the characters' would be as one---i.e. inevitable. Pioneered by Konstantin Stanislavski, currently taught most formally at The Actor's Studio in Manhattan. Of note, most American Method acting was based on an early, incomplete experiment of Stanislavski's; many if not most modern teachers have moved away from the original (Stanislavskian ) "method" as it is truly difficult to teach well, has been altered by many secondary and tertiary disciples in the 60's and 70's to suit personal agendas, and can produce seemingly uninteresting and almost "masturbatory" results in younger actors. Marlon Brando perhaps the best example of a masterful methodist who uses and discards various parts of many school of thought to acieve success.
Motivation: a character's individual desires or goals which propel them into action ;the driving force of an inciting event that starts a story's progression.
Obstacle: a force opposing a character's "Objective" (or "Intention") which gives rise to dramatic tension and conflict.
Objective: a single, temporary desire or goal that arises in a character within a scene. (Also called "Intention".)
Orchestra pit: where the musicians play, usually directly in front of the stage, often sunken below the seating sections
The Orchestra, The Stalls: the seats on the lower part of the theatre
Omnes *: in stage directions, all the cast
Part: a character; the portion of the script intended for one character
Parterre: The upper part of the main seating. Usually behind a cross aisle, and almost always steeper than the lower Orchestra.
Preferred reading: the interpretation of the script that is stressed by the author or the text itself
Protagonist: the main character; the hero or heroine
Pseudomonologue: when only one half of a dialogue is portrayed, especially either just the questions or the answers, wherein the performer is not directly addressing the audience
Script: the text of the dialogue and stage directions of a play; to write a play
Sense memory: in Method acting, when an actor attempts to recall memories of the physical sensations surrounding prior emotions in order to utilize emotional memory
Signs of character: the various cues that convey a character's personality, emotion or motivation
Signs of performance: an actor's movements, expressions and vocal tones and patterns that contribute to signs of character
Social actor: people who portray themselves in a performance, usually previously known to the audience
Stage left: the side of the stage on the left when facing the audience
Stage right: the side of the stage on the right when facing the audience
Standing ovation: at the end of a performance, when the audience stands and claps, a higher form of praise than normal applause
Standing room: a space where people can stand to watch a performance, especially if all the seats are filled (see Gallery). Most New York houses count standing room tickets in their house counts. The Lion King caused quite a stir when it didn't, and boasted more than 100 percent house counts for months.
Standing room only: admittance to a performance after all of the seats are filled which requires people to stand to watch.
Super, Supernumerary: Extra, walk-on part, most often speaks no words.
Supporting cast: actors who are not playing major parts
Typecast: when an actor becomes associated with only one type of role or character, often based on physical appearance
Upstage: towards the back of the stage; the half of the stage that is farthest from the audience; to outshine another's performance, especially when the other has a larger part or is more well-known. (The third meaning derives from the simplest means of "upstaging" another actor: to walk "upstage" of an actor, thereby forcing the other actor to turn his or her back to the audience while the "upstage" actor can stand full front, facing the audience.)
Verisimilitude: the trait of seeming truthful or appearing to be real, from the Latin veri similis, "like the truth"
See also: ballet, Chinese opera, comedy, drama, epic play, farce, kabuki, melodrama, mime, musical theatre, opera, operetta, pantomime, paradigmatic structure, syntagmatic structure, suspension of disbelief, tragedy, tragicomedy, vaudeville